1. Field of the Invention
The present invention relates to multi component catalyst for the hydrogenation of the highly unsaturated compounds comprising Pd and a selected group of modifiers on supports having particular characteristics and process of the hydrogenation of unsaturated hydrocarbons and more particularly the selective hydrogenation of highly unsaturated hydrocarbons such as acetylenes. More particularly the invention relates to the selective hydrogenation of acetylenic compounds in C2-C4 mixed olefin streams.
2. Related Information
Supported palladium and nickel catalysts have been used for various hydrogenation processes for a considerable period of time. Such processes include the selective hydrogenation of acetylenic compounds and dienes in various mixed olefins streams and gasoline and the hydrogenation of benzene.
German patent 2,412,191 discloses the purification of 1,3-butadiene and isoprene streams by the selective hydrogenation of acetylenic compounds using finely dispersed catalyst or supported catalyst. The preferred catalyst metal is either a noble metal such as Pd or non-noble metal such as Co, Fe or Mo. The improvement claimed is that the use of cylcopentadiene improves the 1,3-butadiene selectivity with either noble or non noble catalyst.
It has been well documented that supported Pd catalysts are unstable for selective hydrogenation of vinyl acetylene due to the formation of complex compounds of vinyl acetylene with Pd. The Pd complex compounds are soluble in the hydrocarbon stream. It has been found that the addition of silver to the Pd catalyst results in the stabilization of the catalyst deactivation caused by the loss of Pd metal and an improvement in the selectivity of desired olefin product. See M. L. Derrien et al, Studies in Surface Science and Catalysis, Vol 27, page 613 (1986), and Elsvier and K. James Sasaki, Petrochemicals and Gas Processing, 113 PTQ Autumn, 1997.
U.S. Pat. No. 4,533,779 discloses palladium-gold catalyst supported on supports such as alumina (1 to 100 m2/g) for selective hydrogenation of acetylenic compounds. The alumina used in the examples had a surface area of 70 m2/g, a total pore volume of 0.6 cc/g and an average pore diameter of 200 Å. The deposition of Pd and Au was carried out in two sequential steps. The impregnation of the palladium compound on alumina was carried out using the absorption technique of an organo palladium compound (acetylacetonate) in non-polar organic solvent on alumina. The contents of palladium and gold in the catalysts were in the range of 0.03 to 1 wt % and 0.003 to 0.3 wt %, respectively.
U.S. Pat. No. 4,762,956 discloses a novel catalyst and process for hydrogenation of dienes and acetylene impurities in an olefin feed. The catalyst is a palladium catalyst supported on substantially crystalline alpha alumina whose average pore radius is 200-2000 Å with at least 80% of pores having a pore radius within the range of 100 to 3000 Å. The active palladium metal surface was less than 50 m2/g with an average palladium particle size of at least 25 Å. The impregnation of palladium was carried out by spraying aqueous palladium chloride solution on alumina through an atomizer followed by drying at 80° C.
U.S. Pat. No. 5,866,735 discloses a hydrogenation process using a Pd catalyst supported on a support such as alumina, but modified with alkali iodide such as potassium iodide to reduced the formation of heavy products during the selective hydrogenation of diolefins and/or acetylenic compounds in mixed hydrocarbon streams.
U.S. Pat. No. 5,877,363 discloses the process for the selective hydrogenation of acetylenic impurities and isomerization of 1,2-butadiene to 1,3-butadiene in mixed olefin rich C4 streams by using supported Pt, Pd, etc. catalyst.
European Patent No. 0 567 198 discloses Pd—Cu—K/Al2O3 catalyst for hydrogenation of alkynes and dienes. The preferred catalyst composition is 0.2% Pd, 0.3% Cu and 0.41% K. Preferred alumina support is γ-Al2O3 having 100-250 m2/g surface area and 0.4-0.7 cm3/g pore volume.
U.S. Pat. Nos. 4,644,088 and 4,658,080 disclose acetylene removal processes. The catalyst is multi component catalyst comprising at least Fe and Ni, other elements from Group 8, IB, IIB, IVB, VIB and VIIB of the Periodic Table, an alkaline earth metal and an alkali metal. The catalyst was prepared by mixing dry powders of ZnFe2O4, BaCO3, and NiCO3, followed by kneading the dry mix with aqueous NaOH solution and shaping to appropriate size pellets which were dried. The catalyst comprised a mixture of metal oxides, salts and hydroxides as prepared. The activated working catalyst appears to be mainly composed of metals and metal oxides. Aluminum oxide is not a part of this catalyst. The acetylenes are removed by contacting feeds with catalyst in vapor phase at a range of temperature from 250° to 900° C.
According to V. Rives et al., addition of Zn to Ni—Al Cr oxide catalyst for acetylene hydrogenation in mixed olefin stream hinders coke formation on the catalyst surface and the highest selectivity to ethylene is achieved for Zn/Ni atomic ratio of 4 (Applied Clay Science 13 (1998) 363-379).
A. Sarkany published a paper on egg-shell type Pd and Pd—Ag catalysts supported on alpha alumina for the hydrogenation of 1,3-butadiene (Applied Catalysis: General 175 (1998) 245-253). The deposition of low reactivity heavy hydrocarbons on the catalyst surface causes both the catalyst deactivation and over-hydrogenation to paraffinic products.
H. Uygur et al. published a paper (J. Chem. Eng. Japan, Vol. 31, No 2, 178 (1998)) concerning liquid phase selective hydrogenation of methylacetylene and propadiene (MAPD) in a mixed C3 stream. They found that the conversion of MAPD over 0.3% Pd catalyst decreases as the hydrogenation temperature increases. S. D. Jackson et al. (App. Catalysis A: General 134 (1996) 91-99) found that the adsorption of phenyl acetylene increases with adsorption temperature during their study of the liquid-phase hydrogenation of phenyl acetylene and styrene on a palladium catalyst supported on carbon. N. R. M. Sassen et al. (Faraday Discuss. Chem. Soc., 89 (1998), 331-320) found that the adsorbed ethylidyne species on the Pd (111) increases as temperature raised from −20° C. to 0° C. We found that this is also true for the selective hydrogenation of C3 and C4 acetylenic compounds in a mixed crude butadiene stream over supported Pd—Ag catalyst. This seemingly strange behavior is the result of the combined effect of very low activation energy (<0.5 kcal/mole) of the selective hydrogenation, higher hydrogen solubility in the feed stream at lower temperature and temperature dependency of adsorption of acetylenic compounds on palladium surface in ternary phase reaction system of gas, liquid and solid catalyst. In other words, the concentration of hydrogen in the liquid phase is more influential on the selective hydrogenation rate of acetylenic compounds than the effect of apparent activation energy.